In the course of treating and preparing subterranean oil and gas wells for production, a well packer along with production equipment are run into the well on a tubing string, with the packer being set against a casing bore. Well packers have been designed to accommodate one, two or more production tubing strings. Examples of prior dual string well packers are shown in
U.S. Pat. No. 4,413,677 to Perkins; U.S. Pat. No. 3,167,127 to Sizer; U.S. Pat. No. 3,391,741 to Elliston; and, U.S. Pat. No. 3,381,752 to Elliston. These patents are incorporated herein by reference for all purposes.
The purpose of a dual zone packer is to seal the annulus between the outside of both production tubing strings and the inside of the well casing to prevent movement of fluids through the annulus past that location. The packer is provided with slip anchor members having opposed camming surfaces which cooperate with complementary opposed wedging surfaces, whereby the slip anchor members are extendable radially into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces. The packer also carries annular resilient seal elements which expand radially into sealing engagement against the bore of the well casing in response to axial compression forces. Longitudinal movement of the packer components which set the anchor slips and the sealing elements may be effected either hydraulically or mechanically. During run-in, the packer is mechanically locked in the unset condition by shear pins.
In a dual production zone well, a lower permanent packer with an expendable sealing plug may be set by an electric wire line for isolation of the lower zone after perforating and while working on the upper zone. After perforating the upper zone, the upper production packer is installed. With the use of a dual string hydraulic packer and a pressure-operated circulating sleeve, the completion equipment and the wellhead may be installed before displacing drilling fluid and setting the dual bore packer. Each zone is separately produced through an independent tubing string connected to the dual bore production packer. According to this arrangement, oil or gas from the upper production zone is produced through one of the production tubing strings, and oil or gas from the lower zone is produced through the other tubing string.